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% Scenario 8.6 Failed bank card usage
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\subsection{Scenario 8.6 Failed bank card usage}

This scenario is about the customer who wants to use their bank card to pay at the POS, but the corresponding checking account has an insufficient balance. Because of this the payment fails and this failure is signaled by the POS terminal. This scenario is illustrated in figure \ref{fig:seq_8_6_Failed_bank_card_usage} on page \pageref{fig:seq_8_6_Failed_bank_card_usage}.

Note that POS payments enter the SAB system via SWIFT. The sequence diagram that shows in detail how the incoming SWIFTMessage from the other bank is handled by SAB can be seen in figure \ref{fig:seq_Incoming_SWIFT} on page \pageref{fig:seq_Incoming_SWIFT}. The only difference is that in this case the message goes to the \emph{POS System} in stead of the \emph{Interbank Message Parser}.

There, the POS payment is converted into a Transaction. Once this Transaction is handed to the \emph{Transaction Processing System} it is handled according to the diagram in figure \ref{fig:seq_UC11_Execute_transaction} on page \pageref{fig:seq_UC11_Execute_transaction}. The POS Terminal keeps waiting for the \emph{Transaction Processing System} until a negative reply is received, indicating that the payment debit failed due to an insufficient balance. Only then the payment is acknowledged. Because POS payments get a high priority the wait is very short; 95\% of all payments are confirmed within 10 seconds.

The reply coming from the \emph{Transaction Processing System} will again be sent out through SWIFT which is illustrated in detail in figure \ref{fig:seq_Outgoing_SWIFT} on page \pageref{fig:seq_Outgoing_SWIFT}. The only difference is that in this case the message comes from the \emph{POS System} in stead of the \emph{Interbank Message Generator}.

The use cases touched in this scenario are:
\begin{itemize}
 \item UC13: Issue payment with bank card (alternative flow 3b.)
 \item UC11: Execute transaction (alternative flow 1b.b.)
\end{itemize}

\begin{figure}[!ht]
    \centering
        \includegraphics[angle=90, width=0.55\textwidth]{Scenarios/scenario_img/8_6_Failed_bank_card_usage.png}
    \caption{Failed bank card usage}
    \label{fig:seq_8_6_Failed_bank_card_usage}
\end{figure}

